Endocrine Abstracts

Introduction: Palmitoleate, a proposed adipose tissue (AT)-derived lipokine, has been suggested to contribute to glucose homeostasis. However, data relating to the association between circulating palmitoleate and markers of insulin sensitivity in humans are equivocal. Recently, AT-derived fatty acid-hydroxy fatty acids (FAHFAs) have also been suggested to play a role in glucose homeostasis by increasing glucose uptake in AT. Again, data is conflicting for the association between circulating FAHFAs and markers of insulin sensitivity. The aim of the current work was to clarify the relationships between circulating lipokine concentrations and markers of insulin resistance, using a large cohort of individuals, across a spectrum of adiposity.

Methods: Fasting plasma samples (102 female and 77 male) from healthy, well-phenotyped and non-diabetic participants were stratified, based on the 75th centile of fasting plasma insulin concentrations, as normoinsuliaemic (NI) (n=133) or hyperinsulinaemic (HI) (n=45). Circulating concentrations of plasma palmitoleate were measured using gas chromatography and two FAHFA sub-families (PAHSAs and PAHPAs) were measured by liquid chromatography-mass spectrometry.

Results: We observed female sex-specific, positive correlations (P<0.05) between fasting insulin and PAHSAs and PAHPAs in the HI group only. In both sexes, similar, but non-significant, trends were also observed between circulating palmitoleate concentration and fasting insulin in the HI group, with no trends in the NI group. The HI group had higher relative fat mass, fasting glucose, plasma PAHSA and PAHPA but there were no differences in age, plasma total NEFA or palmitoleate.

Conclusion: Our data suggest that systemic concentrations of palmitoleate may be upregulated in response to insulin insensitivity and, although the same may true of PAHSAs and PAHPAs in females, there is a sexual dimorphic response. However, the usefulness of these lipokines as markers of insulin sensitivity is likely limited as plasma concentrations do not discriminate between individuals classed as NI and HI.